Whereas the reliability of prophylactic devices such as condoms has always been important, the prevalence of AIDS and the alarming increase in unwanted pregnancies has placed even greater emphasis on detecting holes-through which body fluids may pass. At the same time, it is important that the testing for holes be done as economically as possible. Ideally, no defective condoms should pass a test for holes and no acceptable condoms should fail it. It is the understanding of the inventors that the FDA requires testing for holes as small as 10 microns.
A number of testing methods are available. They include a water leak test in which the condom is filled with water and an operator visually checks its outer surface for water droplets. Small holes in the condom result in extremely small water droplets on the surface. These droplets are difficult to see even if the hole location is known before the test is performed. Under actual operating conditions, the failure to detect such a small water droplet could result in the acceptance of a defective condom. Unless extreme care is used, water droplets can be inadvertently deposited on the condom so that acceptable condoms are rejected. Furthermore, it is difficult for an operator to continue to keep a sharp eye out for the droplets. In addition to these difficulties, the inspection of a condom for droplets takes a long time.
Holes can also be detected by electrical methods. In a "wet test", a condom is stretched over a mandrel of conductive material and immersed in a conductive aqueous solution. A low voltage is applied between the mandrel and the solution so that the flow of current in the circuit thus formed indicates a hole. In a "dry test" method, the condom is stretched over a conductive mandrel and conductive brushes or a fine steel screen is placed in contact with the outer surface of the condom. Voltage is applied between the mandrel and the brush or screen so as to produce a current if there is a hole in the condom. But such methods do not work well for condoms made of certain non-latex material, such as polyurethane, for example.
U.S. Pat. No. 5,129,256 describes a method and apparatus for testing condoms by mounting them on a hollow porous mandrel, drawing a partial vacuum in the space within the mandrel and monitoring the interior of the porous mandrel for gas flowing through its walls with a vacuum pressure transducer. It is indicated that preferably the mandrel have an outside diameter that is less than the inside diameter of a condom. The pore openings in the wall are distributed substantially uniformly over its external surface and preferably have a median diameter ranging from ten to fifty microns with a preferred median diameter of twenty microns. The porous part of the mandrel is comprised of a cylindrical body that is closed off at one end, has a wall thickness between 0.04 to 0.50 of an inch and a void volume between 35% and 60%.
If the mandrel is made by sintering particles, fine pores are desired because the dimensions of the walls between pores at the surface of the mandrel are smaller and thus less likely to block a hole in a condom that is stretched over it.